The present invention relates generally to signal processing systems and methods, and more particularly to systems that monitor eye tremor signals.
Presently the diagnosis of brain stem death is made by judging clinical criteria alone such as pupillary response to light, corneal reflex, absent motor response with painful stimulus to both trigeminal distribution and periphery, gag reflex, cough reflex, oculocephalic reflex, vestibule ocular reflex and apnoea test. Clinical evidence alone, which is subject to human error, may not be sufficient to establish such an important diagnosis as brain stem death. Research effort in recent years has been directed to the problem of early prognosis in coma. Accurate early prognosis would allow the concentration of expensive, emotionally draining and time consuming therapeutic measures on patients with a real prospect of recovery. Currently accepted methods of measuring depth of coma include the Glasgow Coma Score (GCS), pupillary responsiveness, systolic hypotension, age, intracranial pressure, radiographic findings, and the vestibulo-ocular reflex (VOR). These methods, however, have not had a widespread impact on clinical management of comatose patients, as the likelihood of false prediction is as high as 20%.
A variety of clinical monitors have also been used in order to assess depth of anesthesia and other brain stem activity including, for example, autonomic signs, EEG, isolated forearm technique, auditory evoked responses, oesophageal contractility and surface EMG, but each method has its limitations. At present, the anesthetist's main source of information on the depth of anesthesia is the patient's somatic and autonomic response to surgical stimuli. These responses are modified by neuromuscular blocking drugs and drugs affecting the autonomic nervous system. The presence or absence of these responses does not, however, correlate with conscious awareness and at times they can be inadequate indicators of a satisfactory depth of anesthesia. Therefore, there is a need for a method and apparatus to adequately measure depth of anesthesia and other conditions correlated with eye tremor.